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CBSE Class 11th Chemistry Notes for Chapter 14 Environmental Chemistry

7/28/2018

UNIT 14 ENVIRONMENTAL CHEMISTRY

ENVIRONMENTAL POLLUTION
Environmental pollution is the effect of undesirable changes in our surroundings that have harmful effects on plants, animals and human beings.
A substance which causes pollution is known as a pollutant.

ATMOSPHERIC POLLUTION
Tropospheric pollution occurs due to:

Gaseous air pollutants
- Oxides of sulphur
- Oxides of nitrogen
- Oxides of carbons, etc.
Particulate air pollutants
- Dust
- Mist
- Fumes
- Smoke
- Smog, etc.

Stratospheric pollution occurs due to chemicals like CFCs breaking down the ozone causing ozone hole.

WATER POLLUTION
Causes of water pollution:

Pathogens: These are the disease causing agents like bacteria and other organisms.
Organic wastes: Organic matter such as leaves, grass, etc. also lead to water pollution.
Chemical pollutants: These include heavy metals, acids, industrial wastes ,etc.

SOIL POLLUTION
Causes:

Pesticides
Soil erosion

GREEN CHEMISTRY
Green chemistry is a way of thinking and is about utilising the existing knowledge and principles of chemistry and other sciences to reduce the adverse impact on environment. Green chemistry is a production process that would bring about minimum pollution or deterioration to the environment.
Green chemistry in day-to-day lives

Dry cleaning of clothes
Bleaching paper
Synthesis of chemicals

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CBSE Class 11th Chemistry Notes for Chapter 13 Hydrocarbons

7/28/2018

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UNIT 13 Hydrocarbons

HYDROCARBONS
Compounds consisting of carbon and hydrogen only are known as hydrocarbons.

ALKANES
These are saturated open chain hydrocarbons containing carbon-carbon single bond.
Properties:
Physical properties:

Alkanes are almost non-polar molecules.
They are colourless and odourless.
Boiling points of alkanes increases with an increase in molecular mass.

Chemical properties:

Substitution reaction: One or more hydrogen atoms of alkanes can be replaced by halogens, nitro group and sulphonic acid group.
Combustion: Alkanes on heating in the presence of air or dioxygen are completely oxidized to carbon dioxide and water with the evolution of large amount of heat.
Controlled oxidation: Alkanes on heating with a regulated supply of dioxygen or air at high pressure and in the presence of suitable catalysts give a variety of oxidation products.
Isomerisation: n-alkanes on heating in the presence of anhydrous aluminium chloride and hydrogen chloride gas isomerise to branched chain alkanes.
Reaction with steam: Methane reacts with steam to form carbon monoxide and dihydrogen.
Pyrolysis: Higher alkanes on heating to higher temperature decompose into lower alkanes, alkenes, etc.

ALKENES
Alkenes are unsaturated hydrocarbons containing at least one double bond.
Isomerism: Alkenes show both structural and geometrical isomerism
Properties:
Physical properties:

Alkenes resemble alkanes in physical properties.
They are, however, different in types of isomerism and difference in polar nature.
Ethene is a colourless gas with a faint sweet smell. All other alkenes are colourless and odourless.

Chemical properties:

Addition of dihydrogen: Alkenes add up one molecule of dihydrogen gas in the presence of finely divided nickel, palladium or platinum to form alkanes.
Addition of halogens: Halogens like bromine or chlorine add up to alkene to from vicinal dihalides.
Addition of hydrogen halides: Hydrogen halides add up to alkenes to form alkyl halides.
Addition of sulphuric acid: Cold concentrated sulphuric acid adds to alkenes in accordance with Markovnikov rule to form alkyl hydrogen sulphate by the electrophilic addition reaction.
Addition of water: In the presence of a few drops of concentrated sulphuric acid alkenes react with water to form alcohols.
Oxidation: Alkenes on oxidation produce vicinal glycols.
Ozonolysis: Ozonolysis of alkenes gives ozonide.

ALKYNES
Alkynes are unsaturated hydrocarbons which contain at least one triple bond between two carbon atoms.
Properties:
Physical properties:

Physical properties of alkynes follow the same trend of alkenes and alkynes.
All alkynes are colourless.
Ethyne has a characteristic odour but other members are odourless.
Alkynes are weakly polar in nature.
They are lighter than water and immiscible with water but soluble in organic solvents like ethers, carbon tetrachloride and benzene.

AROMATIC HYDROCARBON
These hydrocarbons are also known as arenes. Most of these compounds possess a pleasant odour and hence called aromatic.
Most of these compounds contain benzene ring. Benzene ring is highly unsaturated. Aromatic compounds containing benzene ring are known as benzenoids and those not containing a benzene ring are known as non-benzenoids.

Physical properties

Aromatic hydrocarbons are non-polar molecules.
These are usually colourless liquids or solids with a characteristic aroma.
They are immiscible with water.

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CBSE Class 11th Chemistry Notes for Chapter 12 Organic Chemistry

7/28/2018

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UNIT 12 ORGANIC CHEMISTRY

CLASSIFICATION OF ORGANIC COMPOUNDS
1. Acyclic or open chain compounds: These compounds are also called aliphatic compounds and consist of straight or branched chain.
2. Alicyclic or closed chain or ring compounds: These compounds contain carbon atoms joined in the form of a ring.

ISOMERISM
The phenomenon of existence of two or more compounds having the same molecular formula but different properties is known as isomerism. Such compounds are called isomers.
1. Structural isomerism: When compounds have the same molecular formula but different structures, it is called structural isomerism. Types of structural isomerism are:

Chain isomerism: Compounds have similar molecular formula but different carbon skeletons.
Position isomerism: Compounds differ in the position of substituent atom or functional group on the carbon skeleton.
Functional group isomerism: Compounds have the same molecular formula but different functional groups.
Metamerism: Compounds have different alkyl chains on either side of the functional group.

2. Stereoisomerism: When compounds have the same constitution and sequence of covalent bonds but differ in relative positions of their atoms or groups in space, it is known as stereoisomerism.

TYPES OF ORGANIC REACTIONS:

Substitution reactions
Addition reactions
Elimination reactions
Rearrangement reactions

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CBSE Class 11th Chemistry Notes for Chapter 11 The P-Block Elements

7/28/2018

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UNIT 11 THE p-BLOCK ELEMENTS

GROUP 13 ELEMENTS: THE BORON FAMILY

Elements: Boron, Aluminium, Gallium, Indium, Thallium

Electronic configuration: The outer electronic configuration of these elements is ns² np¹.

Atomic radii: Atomic radii increase on going down the group.

Ionization enthalpies: The ionization enthalpies do not decrease smoothly down the group.

Electronegativity: Down the group, electronegativity first decreases from B to Al and then increases marginally.

Physical properties:

Boron is non-metallic in nature. It is extremely hard and black coloured solid. It has an unusually high melting point.
Rest of the members are soft metals with low melting point and high electrical conductivity.
Density of the elements increases down the group from boron to thallium.

Chemical properties:

Reactivity towards air: With oxygen, these elements form their respective oxides. With dinitrogen, they from nitrides.
Reactivity towards acids and alkalis: Boron does not react with acids and alkalis but aluminium dissolves in mineral acids and aqueous alkalis.
Reactivity towards halogens: These elements react with halogens to form trihalides.

GROUP 14 ELEMENTS: THE CARBON FAMILY

Elements: Carbon, Silicon, Germanium, Tin, Lead

Electronic configuration: The valence shell electronic configuration of these elements is ns² np².

Covalent radius: There is a considerable increase in covalent radius from C to Si. From Si to Pb, there is a small increase in radius.

Ionization enthalpy: The first ionization enthalpy of group 14 members is higher than the corresponding members of group 13.

Electronegativity: The elements of this group are slightly more electronegative than group 13 elements.

Physical properties:

All the elements of this group are solid.
Melting points and boiling points of group 14 elements are much higher than those of corresponding elements of group 13.

Chemical properties:

Reactivity towards oxygen: All members when heated with oxygen form oxides.
Reactivity towards water: Carbon, silicon, germanium and lead are unaffected by water but tin forms its dioxide and dihydrogen gas.
Reactivity towards halogen: They form halides with halogens.

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CBSE Class 11th Chemistry Notes for Chapter 10 The S-Block Elements

7/28/2018

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UNIT 10 THE s-BLOCK ELEMENTS

GROUP-1 ELEMENTS: ALKALI METALS

Electric configuration: All alkali metals have one valence electron, 1s².

Atomic and ionic radii: The alkali metal atoms have the largest sizes in a particular period of the periodic table.

Ionization Enthalpy: The ionization enthalpies of the alkali metals are considerable low and decrease down the group.

Hydration Enthalpy: The hydration enthalpies of alkali metal ions decrease as we move down the group.

Physical Properties: All the alkali metals are silvery white, soft and light metals. These elements have low density which increases down the group. The melting and boiling point of alkali metals are low.

Chemical Properties:

Reactivity toward air: The alkali metals tarnish in dry air due to the formation of their oxides which in turn react with moisture to form hydroxides.
Reactivity toward water: Alkali metals react with water to form hydroxide and dihydrogen.
Reactivity towards dihydrogen: Alkali metals react with dihydrogen to form hydride.
Reactivity towards halogens: Alkali metals react vigorously with halogens to form ionic halides.
Reducing nature: The alkali metals are strong reducing agents.
Solutions in liquid ammonia: Alkali metals dissolve in liquid ammonia giving deep blue solutions which are conducting in nature.

Uses:

Lithium is used to make useful alloys. It is also used in thermonuclear reactions and to make electrochemical cells.
Liquid sodium metal is used as coolant in fast breeder nuclear reactor.
Potassium chloride is used as a fertilizer.
Caesium is used in devising photoelectric cells.

GROUP-2 ELEMENTS: ALKALINE EARTH METALS

Electronic configuration: These elements have two electrons in the s-orbital of the valence shell. Their general configuration is ns².

Atomic and ionic radii: The atomic and ionic radii of the alkaline earth metals are smaller than those of the corresponding alkali metals in the same periods.

Ionization enthalpies: Alkaline earth metals have low ionization enthalpies due to fairly large size of the atoms.

Hydration enthalpies: The hydration enthalpies of alkaline earth metals ions decrease with increase in ionic size down the group.

Physical properties:

The alkaline earth metals are silvery white, lustrous and relatively soft but harder than the alkali metals.
The melting and boiling points of these metals are higher than the corresponding alkali metals.

Chemical properties:

Reactivity towards air and water: These metals burn in air to give their oxides and nitrides. They also react with water to form hydroxides.
Reaction with halogens: These metals combine with halogens to form halides.
Reactivity towards hydrogen: These metals react with hydrogen to form their hydrides.
Reactivity towards acids: These metals react with acids liberating dihydrogen.
Reducing nature: Alkaline earth metals are strong reducing agents.
Solutions in liquid ammonia: These metals dissolve in liquid ammonia to give deep blue black solution forming ammoniated ions.

Uses:

Beryllium is used in the manufacture of alloys.
Magnesium alloys are used in aircraft construction.
Calcium is used in the extraction of metal from oxides which are difficult to reduce with carbon.
Radium salts are used in radiotherapy.

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CBSE Class 11th Chemistry Notes for Chapter 9 Hydrogen

7/28/2018

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UNIT 9 HYDROGEN

Hydrogen is the first element in the periodic table.

Its electronic configuration is 1s¹.

DIHYDROGEN, H₂

Occurrence: Dihydrogen is the most abundant element in the universe. It is the principal element in the solar atmosphere.

Isotopes of hydrogen: Hydrogen has three isotopes: protium, deuterium and tritium

PROPERTIES OF DIHYDROGEN:

Physical properties:

It is a colourless, odourless, tasteless, combustible gas.
It is lighter than air.
It is insoluble in water.

Chemical properties

Reaction with halogens: It reacts with halogens to give hydrogen halides.
Reaction with dioxygen: It reacts with dioxygen to form water.
Reaction with dinitrogen: It reacts with dinitrogen to form ammonia.
Reaction with metals: It reacts with metals to yield the corresponding hydrides.
Reaction with metal ions and metal oxides: It reduces some metal ions in aqueous solution and oxides of metals (less active than iron) into corresponding metals.
Reaction with organic compounds: It reacts with organic compounds to give useful hydrogenated products.

USES OF DIHYDROGEN

The largest single use of dihydrogen is in the synthesis of ammonia which is used in the manufacture of nitric acid and nitrogenous fertilizers.
Dihydrogen is used in the manufacture of Vanaspati fat by the hydrogenation of polyunsaturated vegetable oils like soybean, cotton seeds, etc.
It is used in the manufacture of bulk organic chemicals, particularly methanol.
It is widely used for the manufacture of metal hydrides.
It is used for the preparation of hydrogen chloride, a highly useful chemical.
In metallurgical processes, it is used to reduce heavy metal oxides to metals.
Atomic hydrogen and oxy-hydrogen torches find use for cutting and welding purposes.
It is used as a rocket fuel in space research.
It is used in fuel cells for generating electrical energy.

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CBSE Class 11th Chemistry Notes for Chapter 8 Redox Reactions

7/28/2018

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UNIT 8 REDOX REACTIONS

OXIDATION: Loss of electron(s) by any species
REDUCTION: Gain of electron(s) by any species
OXIDISING AGENT: Acceptor of electron(s)
REDUCING AGENT: Donor of electron(s)

REDOX REACTIONS
A reaction in which oxidation and reduction takes place simultaneously is called a redox reaction.

OXIDATION NUMBER
It denotes the oxidation state of an element in a compound ascertained according to a set of rules formulated on the basis that electron in a covalent bond belongs entirely to more electronegative element.

TYPES OF REDOX REACTIONS
1. Combination reactions

In a combination reaction both the elements combining together to form a compound should be in elemental form.

2. Decomposition reactions

A decomposition reaction is the opposite of combination reaction. It leads to the breakdown of a compound into two or more components at least one of which must be in the elemental form.

3. Displacement reactions

In a displacement reaction, an ion (or an atom) in a compound is replaced by an ion (or an atom) of another element.

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CBSE Class 11th Chemistry Notes for Chapter 7 Equilibrium

7/28/2018

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UNIT 7 EQUILIBRIUM

Equilibrium is a state where the rate of evaporation is equal to the rate of condensation.
The mixture of reactants and products in the equilibrium state is called an equilibrium mixture. When there is no change in the concentration s of either of the reactants or the products, the stage is called dynamic equilibrium. At dynamic equilibrium, the rates of forward and backward reaction become equal.

GENERAL CHARACTERISTICS OF EQUILIBRIA INVOLVING PHYSICAL PROCESSES
For physical processes, the following characteristics are common to the system at equilibrium:

Equilibrium is possible only in a closed system at a given temperature.
Both the opposing processes occur at the same rate and there is a dynamic but stable condition.
All measurable properties of the system remain constant.
When equilibrium is attained for a physical process, it is characterised by a constant value of one of its parameters at a given temperature.
The magnitude of such quantities at any stage indicates the extent to which the reaction has proceeded before reaching equilibrium.

LAW OF CHEMICAL EQUILIBRIUM
At a given temperature, the product of concentrations of the reaction products raised to the respective stoichiometric coefficient in the balanced chemical equation divided by the product of concentrations of the reactants raised to their individual stoichiometric coefficients has a constant value. This is known as the Law of chemical equilibrium or Equilibrium law.

APPLICATIONS OF EQUILIBRIUM CONSTANNTS
The important features of equilibrium constants are:

Equilibrium constant is applicable only when concentrations of the reactants and products have attained their equilibrium state.
The value of equilibrium constant is independent of initial concentrations of the reactants and products.
Equilibrium constant is temperature dependent having one unique value for a particular reaction represented by a balanced equation at a given temperature.
The equilibrium constant for the reverse reaction is equal to the inverse of the equilibrium constant for the forward reaction.
The equilibrium constant K for a reaction is related to the equilibrium constant of the corresponding reaction, whose equation is obtained by multiplying or dividing the equation for the original reaction by a small integer.

The following are the applications of equilibrium constant:

To predict the extent of a reaction on the basis of its magnitude.
To predict the direction of the reaction.
To calculate equilibrium concentration.

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CBSE Class 11th Chemistry Notes for Chapter 6 Thermodynamics

7/28/2018

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UNIT 6 THERMODYNAMICS

SYSTEM AND ITS SURROUNDINGS
System: A system in thermodynamics refers to that part of universe in which observations are made.
Surroundings: The surroundings include everything other than the system.

TYPES OF SYSTEM
1. Open system

In an open system, there is exchange of energy and matter between system and surroundings.

2. Closed system

In a closed system, there is no exchange of matter, but exchange of energy is possible between system and surroundings.

3. Isolated system

In an isolated system, there is no exchange of energy or matter between the system and the surroundings.

THE STATE OF THE SYSTEM
The state of a thermodynamic system is described by its measurable or macroscopic (bulk) properties. The state can be described by quoting its pressure, volume, temperature, etc. Variables like these are called state variables or state functions because their values depend only on the state of the system and not on how it is reached.

THE INTERNAL ENERGY AS A STATE FUNCTION
The internal energy of a system may change due to heat passing in or out of the system, work done on or by the system, or if matter enters or leaves the system.
ENTROPY
Entropy is a measure of disorder or randomness in a system.

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